Herbicidal 2-fluoro-4-halo-phenyl-4,5,6,7-tetrahydro-2h-isoindole-1,3-diones

ABSTRACT

This invention relates to herbicidal 2-fluoro-4-halo-phenyl-4,5,6,7-tetrahydro-2H-isoindole-1,3-diones. These compounds may be used for selective weed control in certain crops or for total vegetation control.

RELATED APPLICATION

This application is a continuation-in-part of my earlier filedapplication U.S. Ser. No. 502,968 filed Sept. 3, 1974, now abandoned,entitled2-(4-CHLORO-2-FLUOROPHENYL)-4,5,6,7-TETRAHYDRO-2H-ISOINDOLE-1,3DIONE AND2-(4-BROMO-2-FLUOROPHENYL)-4,5,6,7-TETRAHYDRO-2H-ISOINDOLE-1,3-DIONE ANDTHEIR USE AS HERBICIDES.

BACKGROUND OF THE INVENTION

A number of isoindole-type compounds are known in the prior art.Recently, in German Offenlegungsschrift No. 2,165,651 a group ofisoindole-1,3 -diones which are useful as herbicides was disclosed. Thegeneral formula for the isoindole-1,3-diones is as follows: ##SPC1##

Wherein R may be an aryl, aralkyl or benzyl optionally substituted with1 to 5 halogen atoms; hydroxy, nitro, cyano, thiocyano, carboxy,halogenated alkyl, or alkyl, or alkoxy, lower alkylthio, phenylgroupings and a group having the configuration --O--CH₂ A may also besubstituted therein, wherein A is a phenyl or a naphthyl group, whereinthe phenyl group may have one or more substitutions therein, such ashalogen atoms, nitro groupings, lower alkyl groupings or lower alkoxygroupings.

Typical of the compounds disclosed in the Offenlegungsschrift is thecompound of Example 1: ##SPC2##

It should be emphasized that several thousand compounds are disclosedwithin the broad description of the Offenlegungsschrift.

The compounds of the present invention result from efforts to developsuperior herbicidal compounds.

SUMMARY OF THE INVENTION

This invention relates to novel compounds of the following formula andtheir use as herbicides: ##SPC3##

Wherein X is Cl, Br or F, and Y is H or F, provided that when X is F, Yis F. It is preferred that X is Cl and Y is H.

This invention also includes herbicidal compositions containing theabove compounds as active ingredients and methods of controllingundesirable vegetation by applying the compounds and/or compositions tothe locus of such undesired vegetation.

DESCRIPTION OF THE INVENTION

Preferred compounds

The preferred compound of the instant invention is2-(4-chloro-2-fluorophenyl)-4,5,6,7-tetrahydro-2H-isoindole-1,3-dione.

Synthesis of the compounds

The compounds of Formula I can be made by the processes described andexemplified below.

The preparation of the subject compounds begins with 2-fluoroaniline and2'-fluoro-acetanilide, which can be prepared as described by G.Schiemann and H. G. Baumgarten, Chem. Berichte, 70; 1416 (1937). Theprocess to be utilized in order to form the compounds of the instantinvention is as follows: ##SPC4## ##SPC5##

Wherein X is Cl, Br or F, and Y is H or F, provided that when X is F, Yis F. It is preferred that X is Cl and Y is H.

Step A

The reaction of 2'-fluoroacetanilide and chlorine in acetic acid is wellknown to those skilled in the art, e.g., W. W. Reed and K. J. P. Orton,J. Chem. Soc., 91, 1543 (1907) for the chlorination of acetanilide toobtain 2',4'-dichloroacetanilide. The reaction takes place at 25°-30°Cover several hours at atmospheric pressure.

Step B

The chlorofluoroacetanilide is refluxed in a mixture of a lower alcohol(50%) and concentrated hydrochloric acid (50%) for several hours at70°-90°C and atmospheric pressure. The solvent mixture is removed at areduced pressure of 100 to 300 mm.Hg and 20°-50°C to leave a residue ofthe hydrochloride salt of 4-chloro-2-fluoroaniline.

Step C

By treatment of an aqueous solution of the hydrochloride salt of4-chloro-2fluoroaniline with an alkali metal hydroxide solution, thefree 4-chloro-2-fluoroaniline is extracted into a suitablewater-immiscible organic solvent such as ethyl ether or methylenechloride. The crude 4-chloro-2-fluoroaniline is isolated by removal ofthe organic solvent under reduced pressure of 100 to 300 mm.Hg. at20°-50°C.

Step A'

The reaction of 2-fluoroaniline and N-bromosuccinimide in an inertorganic solvent such as methylene chloride is well known to thoseskilled in the art, e.g., J. B. Wommack et al., J. Het. Chem., 6, 243(1969). The exothermic reaction takes place at 0°C over several hours.The resulting reaction mixture is washed with water several times anddried with an appropriate drying agent such as anhydrous sodium sulfate.The 4-bromo-2-fluoroaniline is recovered by removal of the organicsolvent under reduced pressure of 100 to 300 mm.Hg. at 20°-50°C.

Step A"

The synthesis of 2,4,6-trifluoroaniline from1,3,5-trifluoro-2-nitrobenzene uses the same procedure as that describedby G. Schiemann and M. Seyhan [chem. Ber., 70, 2396 (1937)] for thepreparation of 2,4-difluoroaniline. The preparation of1,3,5-trifluoro-2-nitrobenzene is described by V. I. Siele and H. J.Matsuguma, U.S. Dept. Com., Office Serv., P B Rept. 145, 510, p. 1(1960) [Chem. Abst. 56, 15394C (1962)].

Step D

The reaction of each of the di- or trihalo anilines (from Step C, A' orA") and 3,4,5,6-tetrahyrophthalic anhydride in acetic acid to form thecorresponding imide is demonstrated in Netherlands Pat. No. 7,117,690(Mitsubishi Chem. Ind.). The dihaloaniline and3,4,5,6-tetrahydrophthalic anhydride are refluxed in glacial acetic acidat temperatures of 115°-120°C and atmospheric pressure for severalhours. The di- ortrihalophenyl-4,5,6,7-tetrahydro-2H-isoindole-1,3-dione is isolated byprecipitation with water followed by filtration.

The compounds which may be prepared by the instant process are asfollows:

2-(4-chloro-2-fluorophenyl)-4,5,6,7-tetrahydro-2H-isoindole-1,3-dionem.p. 76.5°-78.0°C

2-(4-bromo-2-fluorophenyl)-4,5,6,7-tetrahydro-2H-isoindole- 1,3-dionem.p. 102.0°-102.5°C

2-(2,4-difluorphenyl)-4,5,6,7-tetrahydro-2H-isoindole-1,3-dione m.p.73°-74°C

2-(2,4,6-trifluorophenyl)-4,5,6,7-tetrahydro-2H-isoindole-1,3-dione m.p.91°-92°C

The following examples further illustrate this method for synthesis ofcompounds of this invention. All parts are by weight and alltemperatures in degrees centigrade unless otherwise indicated.

EXAMPLE 1 Preparation of2-(4-chloro-2-fluorophenyl)-4,5,6,7-tetrahydro2H-isoindole-1,3-dione

A solution of 140 parts of 2'-fluoroacetanilide in 500 parts glacialacetic acid was treated with 71 parts of chlorine during one hour at25°-27°C with ice-water cooling. While stirring for 4 hours at 25°-27°C,4'-chloro-2'-fluoroacetanilide precipitated. After collecting theproduct by filtration, the filtrate was poured over 2000 parts of ice.The resulting second portion of product precipitated was collected byfiltration, combined with the first portion and recrystallized from 700parts of methanol at -45°C. to yield 119 parts of4'-chloro-2'-fluoroacetanilide as white crystals melting at 152°-155°C.

A mixture of 119 parts of 4'-chloro-2'-fluoroacetanilide in 475 parts ofethanol and 200 parts of 37% hydrochloric acid was refluxed for 17 hoursand the solvent removed under a reduced pressure of 300 mm.Hg. to yieldthe moist, solid hydrochloride salt of 4-chloro-2-fluoroaniline.

The moist, solid hydrochloride salt of 4-chloro-2-fluoroaniline wascooled in an ice-acetone bath and treated at 10°C with 50% aqueoussodium hydroxide until pH 11 is reached. The resulting two-phase mixturewas extracted four times; 500 parts of methylene chloride were used foreach extraction. The combined organic extracts were dried with anhydroussodium sulfate and the solvent removed under reduced pressure of 300mm.Hg. to leave 89 parts of light brown, oily 4-chloro-2-fluoroaniline,N_(D) ²⁵ = 1.5541.

A solution of 88 parts of 3,4,5,6-tetrahydrophthalic anhydride in 2000parts of glacial acetic acid was treated with 84 parts of4-chloro-2-fluoroaniline at once and stirred for one hour. Afterrefluxing for 19 hours, 1000 parts of acetic acid were distilled fromthe reaction mixture. The residue from the distillation was poured over3000 parts of ice. The resulting crystals were filtered andrecrystallized from 700 parts of methanol at -40°C after activatedcarbon treatment, to yield 117 parts off-white crystals of2-(4-chloro-2-fluorophenyl)-4,5,6,7-tetrahydro-2H-isoindole-1,3dionemelting at 76.5°-78.0°C.

EXAMPLE 2 Preparation of2-(4-bromo-2-fluorophenyl)-4,5,6,7-tetrahydro-2H-isoindole-1,3-dione

A solution of 100 parts of 2-fluoroaniline in 400 parts of methylenechloride was cooled to 0°C and treated batchwise with 160 parts of solidN-bromosuccinimide over 2 hours at 0°C. After stirring for 20 minutes,the dark red mixture was washed four times; 200 parts of cold water wereused for each washing. The red organic phase was dried with anhydroussodium sulfate and evaporated under 300 mm.Hg. to 164 parts of brown,oily 4-bromo-2-fluoroaniline, N_(D) ²⁵ : 1.5885.

A solution of 10 parts of 3,4,5,6-tetrahydrophthalic anhydride in 100parts of glacial acetic acid was treated in one portion with 11 parts of4-bromo-2-fluoroaniline and was stirred for 30 minutes. The reactionmixture was refluxed for 16 hours and then poured over 200 parts ice.The resulting purple crystals were filtered and recrystallized from 100parts methanol at -40°C to yield 13 parts of pink plates of2-(4-bromo-2-fluorophenyl)-4,5,6,7-tetrahydro-2H-isoindole-1,3-dionemelting at 102.0°-102.5°C.

EXAMPLE 3

A solution of 5 parts of 3,4,5,6-tetrahydrophthalic anhydride in 100parts of glacial acetic acid was treated with 4.3 parts of2,4-difluoroaniline at once and stirred for one hour. After refluxingfor 20 hours, the reaction mixture was poured over 200 parts of ice. Theresulting crystals were filtered and recrystallized from 70 parts ofmethanol at -40°C to yield 5 parts off-white crystals of2-(2,4-difluorophenyl)-4,5,6,7-tetrahydro-2H-isoindole-1,3-dione meltingat 73°-74°C.

EXAMPLE 4

A solution of 5.3 parts of 3,4,5,6-tetrahydrophthalic anhydride in 100parts of glacial acetic acid was treated with 5 parts of2,4,6-trifluoroaniline at once. After refluxing for 24 hours, the aceticacid was stripped from the reaction mixture under 300 mm hg pressure.The residue was dissolved in 100 parts of methylene chloride and washedwith 100 parts of 10% aqueous sodium carbonate. After drying overanhydrous sodium sulfate, the solution was stripped under 300 mm hgpressure. The resulting pink oil was crystallized from 70 parts ofmethanol at -40°C to yield 4.7 parts white crystals of2-(2,4,6-trifluorophenyl)-4,5,6,7-tetrahydro-2H-isoindole-1,3-dionemelting at 91°-92°C.

FORMULATIONS OF THE COMPOUNDS

The formulations of the compounds of Formula I for use in this inventioncan be prepared in conventional ways. They include dusts, granules,pellets, solutions, suspensions, emulsions, wettable powders,emulsifiable concentrates, and the like. Many of these can be applieddirectly. Sprayable formulations can be extended in suitable media andused at spray volumes of from a few pints to several hundred gallons peracre. High strength compositions are primarily used as intermediates forfurther formulation. The formulations, broadly, contain about 1% to 99%by weight of active ingredient(s) and at least one of (a) about 0.1% to20% surfactant(s) and (b) about 5% to 99% solid or liquid diluent(s).More specifically, they will contain these ingredients in the followingapproximate proportions.

    ______________________________________                                                      Active %                                                                              %        %                                                            Ingredient                                                                            Diluent  Surfactant                                     ______________________________________                                        Wettable Powders                                                                              20-90      0-74    1-10                                       Oil Suspensions                                                               Emulsions, Solutions                                                          (Including Emulsifiable                                                       Concentrates)    5-50     40-95    0-10                                       Aqueous Suspensions                                                                           10-50     40-89    1-10                                       Dusts            1-25     70-99    0-5                                        Granules and Pellets                                                                           1-35     65-99    0-15                                       High Strength Compositions                                                                    90-99      0-10    0-2                                        ______________________________________                                    

Lower or higher levels of active ingredient can, of course, be presentdepending on the intended use and the physical properties of thecompound. Higher ratios of surfactant to active ingredient are sometimesdesirable and are achieved by incorporation into the formulation or bytank mixing.

The compounds of Formula I can be combined with other herbicides and areparticularly useful in combination with bromacil[3-(sec-butyl)-5-bromo-6-methyluracil],diuron-[3-(3,4-dichlorophenyl)-1,1-dimethylurea],paraquat[1,1'-dimethyl-4,4'-bipyridinum ion],m-(3,3-dimethylureido)-phenyl tert-butylcarbamate,4-amino-6-tert-butyl-3-methylthio-as-triazin-5(4H)-one, and thes-triazines such as 2-chloro-4-ethylamino-6-isopropylamino-s-triazine,for controlling a broad spectrum of weeds.

Typical solid dilutents are described in Watkins et al. "Handbook ofInsecticide Dust Diluents and Carrier", 2nd Edition, Dorland Books,Caldwell, New Jersey. The more absorptive diluents are preferred forwettable powders and the denser ones for dusts. Typical liquid diluentsand solvents are described in Marsden "Solvents Guide", 2nd Edition,Interscience, New York, 1950. Solubility under 0.1% is preferred forsuspension concentrates; solution concentrates are preferably stableagainst phase separation at 0°C. "McCutcheon's Detergents andEmulsifiers Annual" Allured Publishing Corporation, Ridgewood, NewJersey, as well as Sisely and Wood "Encyclopedia of Surface-ActiveAgents", Chemical Publishing Co., New York, 1964, lists surfactants andrecommended uses. All formulations can contain minor amounts ofadditives to reduce foam, caking, corrosion, microbiological growth,etc. Preferably, ingredients should be approved by the U.S.Environmental Protection Agency for the use intended.

The methods of making such compositions are well known. Solutions areprepared by simply mixing the ingredients. Fine solid compositions aremade by blending and usually grinding as in a hammer or fluid energymill. Suspensions are prepared by wet milling (see, for example, LittlerU.S. Pat. No. 3,060,084). Granules and pellets can be made by sprayingthe active material upon preformed granule carriers or by agglomerationtechniques (see J. E. Browning "Agglomeration", Chemical Engineering,Dec. 4, 1967, pages 147 ff. and "Perry's Chemical Engineer's Handbook",4th Edition, McGraw-Hill, New York, 1963, pages 8-59 ff.

For further information regarding the art of formulation see, forexample:

H. m. loux, U.S. Pat. No. 3,235,381, Feb. 15, 1966 Column 6, line 16through column 7, line 19, and examples 10-41.

R. w. luckenbaugh, U.S. Pat. No. 3,309,192, Mar. 14, 1967, Column 5,line 43 through column 7, line 62, and examples 8, 12, 15, 39, 41, 52,53, 58, 132, 138-140, 162-164, 166, 167, and 169-182.

H. gysin and E. Knusli, U.S. Pat. No. 2,891,855, June 23, 1959, Column3, line 66 through column 5, line 17 and examples 1 through 4.

G. c. klingman, "Weed Control as a Science", John Wiley & Sons, Inc.,New York, 1961, pages 81 through 96.

J. d. fryer and S. A. Evans, "Weed Control Handbook", 5th Edition,Blackwell Scientific Publications, Oxford, 1968, pages 101-103.

The following examples illustrate formulations of this invention. Allparts are by weight unless otherwise indicated.

EXAMPLE 5

    Wettable Powder                                                               2-(4-chloro-2-fluorophenyl)-4,5,6,7-                                          tetrahydro-2H-isoindole-1,3-dione                                                                        50%                                                Kaolinite                  38%                                                Diatomite                  5%                                                 Synthetic silica           3%                                                 Sodium ligninsulfonate     2%                                                 Sodium alkylnaphthalenesulfonate                                                                         2%                                             

The ingredients are blended, hammermilled to a fine powder,substantially all of which will pass through a 50-mesh sieve, andreblended.

EXAMPLE 6

    Wettable Powder                                                               2-(4-bromo-2-fluorophenyl)-4,5,6,7-                                           tetrahydro-2H-isoindole-1,3-dione                                                                        50%                                                Kaolinite                  46%                                                Sodium alkylnaphthalenesulfonate                                                                         2%                                                 Low viscosity methyl cellulose                                                                           2%                                             

The ingredients are blended, hammermilled to a fine powder,substantially all of which will pass through a 50-mesh sieve, and thenreblended.

EXAMPLE 7

    Wettable Powder                                                               2-(2,4-difluorophenyl)-4,5,6,7-tetrahydro-                                                                50%                                               2H-isoindole-1,3-dione                                                        Kaolinite                   46%                                               Sodium alkylnaphthalenesulfonate                                                                          2%                                                Low viscosity methyl cellulose                                                                            2%                                            

The ingredients are blended, hammermilled to a fine powder,substantially all of which will pass through a 50-mesh sieve, and thenreblended.

EXAMPLE 8

    Wettable Powder                                                               2-(2,4,6-trifluorophenyl)-4,5,6,7-tetrahydro-                                                             50%                                               2H-isoindole-1,3-dione                                                        Kaolinite                   46%                                               Sodium alkylnaphthalenesulfonate                                                                          2%                                                Low viscosity methyl cellulose                                                                            2%                                            

The ingredients are blended, hammermilled to a fine powder,substantially all of which will pass through a 50-mesh sieve, and thenreblended.

UTILITY

The compounds of formula I are useful for the selective preemergenceweed control of undesired vegetation such as rice, soybeans, peanuts,lima beans, green beans and squash. These compounds also have utilityfor the postemergence control of weeds in certain crops, for example,carrots. Furthermore, compounds of this invention can be used asdirected treatments for the pre/post-emergence control of weeds invarious crops including soybeans, peanuts, garden beans and row-plantedrice. In addition, these compounds are useful wherever general weedcontrol is required, such as industrial sites, railroad and utilityrights-of-way, along fences, building foundations, parking and storagelots, etc.

The precise amount of the compounds of formula I to be used in any givensituation will vary according to the particular end result desired, theuse involved, the plant and soil involved, the formulation used, themode of application, prevailing weather conditions, foliage density andlike factors. Since so many variables play a role, it is not possible tostate a rate of application suitable for all situations. Broadlyspeaking, the compounds of the invention are used at levels of about0.125 to about 20 kilograms, preferably about 0.25 to about 10, perhectare. The lower rates in this range will generally be selected onlighter soils, soils low in organic matter content, for selective weedcontrol in crops, or in situations where maximum persistence is notnecessary.

Herbicial activity of compounds of this invention was discovered in anumber of field tests.

In test A, soybeans, peanuts, lima beans, green beans and squash wereplanted in a field infested with the following weed seeds: crabgrass(Digitaria sanquinalis), foxtails (Setaria spp.), barnyardgrass(Echinochloa crusgalli), pigweed (Amaranthus spp.), ragweed (Ambrosiaartemisiifolia), velvetleaf (Abutilon theophrasti), purslane (Portulacaoleracea) and flower-of-an-hour (Hibiscus trionum). A 50% wettablepowder formulation of2-(4-chloro-2-fluorophenyl)-4,5,6,7-tetrahydro-2H-isoindole-1,3-dionewas applied in the form of an aqueous suspension at rates of 0.125,0.25, 0.5 and 1.0 kg/ha, each treatment replicated twice. The plots wererated for percent weed control and crop response seven weeks aftertreatment. Crop response was expressed on a scale of 0 = no injury to 10= complete kill. The results obtained are shown in the following table.

                                      TABLE I                                     __________________________________________________________________________    TEST A                                                                        % Control                                Crop Response                        Rate Crab-                                                                             Fox-                                                                             Barnyard-                                                                           Pig-                                                                             Rag-          Flower-of-                                                                             Green                                                                              Lima                         kg/ha                                                                              grass                                                                             tail                                                                             grass weed                                                                             weed                                                                             Velvetleaf                                                                          Purslane                                                                           an-Hour                                                                             Squash                                                                           beans                                                                              beans                                                                             Peanuts                                                                            Soybeans            __________________________________________________________________________    0.125                                                                              60  40 45    90 90  90    82  87    2   2   0   0    0                   0.25 94  82 82    98 99  99    97  99    2   2.5 1   0    1.5                 0.50 99  95 98    95 99 100   100  99    6   8   4   2    3                   1.00 99  99 99    100                                                                              100                                                                              100   100  100   9.5 8.5 8.5 3.5  7.5                 __________________________________________________________________________

Test B involved a field sown to carrots and in which the following weedspecies emerged naturally: crabgrass (Digitaria sanquinalis), foxtails(Setaria spp.), barnyardgrass (Echinochloa crusgalli), pigweed(Amaranthus spp.), ragweed (Ambrosia artemisiifolia), velvetleaf(Abutilon theophrasti), smartweed (Polygonum spp.) and lambsquarters(Chenopodium album). Sixteen days after sowing, when all species ofweeds had emerged, the plants were sprayed overall with a 50% wettablepowder formulation of2-(4-chloro-2-fluorophenyl)4,5,6,7-tetrahydro-2H-isoindole-1,3dione(Treatment I) in the form of an aqueous suspension, at rates of 0.5,1.0, 2.0 and 4.0 kg/ha, and with2-(4-chlorophenyl)-4,5,6,7-tetrahydro-2H-isoindole-1,3-dione (TreatmentII) in the same form and at the same rates. The spray volume was 425l/ha. The surfactant Tween 20* was added to all treatments in aconcentration of 0.1% by weight. Six weeks after treatment, visualobservations were made of percent weed control obtained and, forcarrots, crop response. Pertinent data are presented in the followingTable II.

                                      TABLE II                                    __________________________________________________________________________    TEST B                                                                        TREATMENT                                                                             % Control                                      Crop Response          I       Naturally Emerging Weeds                                              Rate                Barnyard-                     Lambs-                      kg/ha   Crabgrass                                                                           Foxtails                                                                            grass Pigweed                                                                             Ragweed                                                                             Velvetleaf                                                                          Smartweed                                                                           quarters                                                                           Carrots                __________________________________________________________________________    0.5     60    70    65    92  98      100    99+  100  2                      1.0     85    90    90    99   99+    100   100   100  3                      2.0     90    94    94    100 100     100   100   100  5                      4.0     100    99+   99+  100 100     100   100   100  6                      TREATMENT                                                                     II                                                                            Rate                                                                          kg/ha                                                                         0.5      0     0     0    50  50       70   70     70  4                      1.0     20    20    20    70  70       80   80     80  4                      2.0     40    40    40    90  90      100   80     99  4                      4.0     60    40    50    99   99+    100   99     99  4                      __________________________________________________________________________

The superiority of Treatment I was quite pronounced with respect to thenaturally emerging weeds. In every one of the eight tests Treatment Iproduced % control results which were clearly superior to Treatment II.In particular, the control of crabgrass, foxtails and barnyardgrass withTreatment I was outstanding when compared to Treatment II.

Test C concerned preemergence weed control in rice. The field selectedcontained seeds of the following weed species: crabgrass (Digitariasanquinalis), foxtail (Setaria spp.), barnyardgrass (Echinochloacrusgalli), pigweed (Amaranthus spp.), ragweed (Ambrosiaartemisiifolia), velvetleaf (Abutilon theophrasti), purslane (Portulacaoleracea) and flower-of-an-hour (Hibiscus trionum). Two varieties ofrice, CSM-3 and Nato, were planted at depths of both 1 and 2 cm. Inaddition, rice seedlings of both varieties were transplanted into thefield to be treated. Immediately thereafter, the plot was treated withan aqueous suspension of2-(4-chloro-2-fluorophenyl)-4,5,6,7-tetrahydro-2H-isoindole-1,3-dione(Treatment I) at rates of 0.125 and 0.25 kg/ha, and an aqueoussuspension of2-(4-chlorophenyl)-4,5,6,7-tetrahydro-2H-isoindole-1,3dione (TreatmentII) at rates of 0.25, 0.50, 1.00 and 2.00 kg/ha. The test chemicals hadbeen formulated as 50% wettable powders. Overall spray volume was 540l/ha. Ratings of percent weed control obtained and crop response weremade 29 days after treatment, as described for test A. The ratings aresummarized in the following Table III.

                                      TABLE III                                   __________________________________________________________________________    TEST C                                                                        TREATMENT                                  Crop Response                      I       % Control                          Rice                               Rate    Crab-                                                                             Fox-                                                                             Barnyard-                                                                           Pig-                                                                             Rag-                                                                             Velvet-   Flower-of-                                                                          CSM-3     Nato                     kg/ha   grass                                                                             tail                                                                             grass weed                                                                             weed                                                                             leaf Purslane                                                                           an-Hour                                                                             1 cm*                                                                             2 cm*                                                                             T*                                                                              1 cm*                                                                             2                                                                                 T**              __________________________________________________________________________    0.125    96  96                                                                              90     99                                                                              100                                                                              100  100  100   3   0   0 3   1   0                0.25    100 100                                                                              99    100                                                                              100                                                                              100  100  100   5   1   0 6   2   0                TREATMENT                                                                     II                                                                            Rate                                                                          kg/ha                                                                         0.25     99  99                                                                              58    100                                                                              100                                                                              100  100   98   4   1   0 5   0   1                0.50    100 100                                                                              97    100                                                                              100                                                                              100  100  100   5   2   0 8   1   1                1.0     100 100                                                                              99    100                                                                              100                                                                              100  100  100   7   4   0 9   4   1                2.0     100 100                                                                              100   100                                                                              100                                                                              100  100  100   10  7   1 9   6   2                __________________________________________________________________________     *1 cm and 2 cm = pl. depth;                                                   T = transplanted.                                                        

What is claimed is:
 1. The compound2-(4-chloro-2-fluorophenyl)-4,5,6,7-tetrahydro-2H-isoindole-1,3-dione.2. The compound2-(4-bromo-2-fluorophenyl)-4,5,6,7-tetrahydro-2H-isoindole-1,3-dione. 3.The compound2-(2,4-difluorophenyl)-4,5,6,7-tetrahydro-2H-isoindole-1,3-dione.